This revised application requests a second 5-year period of support for a program project having the following general goals: (1) to assess the utility of approaches, instrumentation, and analysis procedures designed to enable identification and quantification of central somatosensory nervous system adaptive mechanisms in normal human subjects as well as in patient populations with orofacial sensory dysfunction; and (2) to evaluate experimentally the hypothesis that in a variety of orofacial sensory disorders (including temporomandibular disorders - TMD) the dynamic neural mechanisms which normally operate to adaptively modify the somatosensory cerebral cortical response to maintained ("tonic") somatic afferent drive function in an abnormal and maladaptive manner. The skills, prior experiences, and interests of the participating investigators are consistent with the goals proposed: collectively, the assembled research team possesses a considerable record of contributions to somatosensory neurophysiology and human psychophysics, and includes appropriate expertise in the evaluation, management, and treatment of clinical pain populations. The program involves five independent, but inter-related projects, all interacting closely with a core designed (1) to provide the number of thoroughly screened, adequately protected, and fully clinically- characterized human subjects required to satisfy project and program goals, (2) to make readily available to each project high quality and appropriate statistical and computational support, (3) to stimulate sharing and integration of the information obtained by the different projects and interpretation of that information in terms of the neural mechanisms underlying chronic orofacial sensory dysfunction, and finally, (4) to provide essential administrative support, coordination, and scientific leadership.